netdev - Re: [PATCH bpf-next] bpf: Enforce 'return 0' in BTF-enabled raw

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Date:   Tue, 29 Oct 2019 04:32:22 +0000
From:   Andrii Nakryiko <andriin@...com>
To:     Alexei Starovoitov <ast@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>
CC:     "daniel@...earbox.net" <daniel@...earbox.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "Kernel Team" <Kernel-team@...com>
Subject: Re: [PATCH bpf-next] bpf: Enforce 'return 0' in BTF-enabled raw_tp
 programs

On 10/28/19 8:24 PM, Alexei Starovoitov wrote:
> The return value of raw_tp programs is ignored by __bpf_trace_run()
> that calls them. The verifier also allows any value to be returned.
> For BTF-enabled raw_tp lets enforce 'return 0', so that return value
> can be used for something in the future.
> 
> Signed-off-by: Alexei Starovoitov <ast@...nel.org>
> ---

Looks good, if the return value is ignored, no need to specify anything 
but 0 for now.

Acked-by: Andrii Nakryiko <andriin@...com>

>   kernel/bpf/verifier.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index c59778c0fc4d..6b0de04f8b91 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -6279,6 +6279,11 @@ static int check_return_code(struct bpf_verifier_env *env)
>   	case BPF_PROG_TYPE_CGROUP_SYSCTL:
>   	case BPF_PROG_TYPE_CGROUP_SOCKOPT:
>   		break;
> +	case BPF_PROG_TYPE_RAW_TRACEPOINT:
> +		if (!env->prog->aux->attach_btf_id)
> +			return 0;
> +		range = tnum_const(0);
> +		break;
>   	default:
>   		return 0;
>   	}
>